Apparatus for preserving hydrophilic gels,more particularly ocular contact lenses

ABSTRACT

APPARATUS FOR THE STORAGE OF A SWELLABLE HYDROPHILIC POLYMERIC GEL BODY SUCH AS A CRONTACT LENS OR OTHER IMPLANT COMPRISES A LIQUID CONTAINER DIVIDED INTO AT LEAST TWO PARTS BY A POROUS WALL AND HAVING A PHYSIOLOGIC LIQUID CONTAINED THEREIN, ONE OF SAID CONTAINER PARTS BEING ADAPTED TO HOLD SAID GEL BODY IMMERESED IN SAID LIQUID, A CATION RESIN EXCHANGE MATEIAL IMPREGNATED WITH A SURFACE ACTIVE METALLIC SILVER, SAID MATERIAL BEING LOCATED IN THE OTHER OF THE CONTAINER PARTS AND BEING SOLUBLE BY SAID LIQUID TO RELEASE SURFACE SILVER IONS OVER A PERIOD OF TIME TO THEREAFTER, FREELY FLOW THROUGH SAID POROUS WALL INTO CONTACT WITH SAID GEL BODY.

United States Patent 3,591,329 APPARATUS FOR PRESERVING HYDROPHELICGELS, MORE PARTICULARLY OCULAR CON- TACT LENSES Richard Chromecek, anVodr iansky, and Jiii Manych, Prague, Czechoslovakia, assignors toCeskoslovenska akademie ved, Prague, Czechoslovakia No Drawing. FiledMar. 13, 1968, Ser. No. 712,609 Claims priority, applicationCzechoslovakia, Mar. 15, 1967, 1,883/67 Int. Cl. A611 3/00 US. Cl.21--6l Claims ABSTRACT OF THE DISCLOSURE Apparatus for the storage of aswellable hydrophilic polymeric gel body such as a contact lens or otherimplant comprises a liquid container divided into at least two parts bya porous Wall and having a physiologic liquid contained therein, one ofsaid container parts being adapted to hold said gel body immersed insaid liquid, a cation resin exchange material impregnated with a surfaceactive metallic silver, said material being located in the other of thecontainer parts and being soluble by said liquid to release surfacesilver ions over a period of time to thereafter, freely flow throughsaid porous wall into contact with said gel body.

The present invention relates to a protective system for preserving andstoring swelled hydrophilic polymeric gels as well as articles madetherefrom, more particularly ocular contact lenses, which systemconsists of a room to receive hydrogel, separated by a permeable wallfrom a room designed for cation exchanger on which silver has beenreduced.

In many cases hydrophilic gels have to be preserved or stored in swelledcondition, most frequently under water or physiologic solution. In thismanner hydrophilic gels are easily liable to get perished which iscaused preponderantly by mildew organisms or fungi which grow not onlyon the surface of the gel but also through its interior and lead topermanent, irreversible degradation thereof. Fungi cause particulartroubles in the preparation and application of ocular contact lenses onthe basis of glycolmethacrylate gels. The degradation influenced by thegrowth of fungi is of an irreparable character so that it cannot besuppressed by any of conventional means. The possibility of mildewgrowth on hydrophilic gels, especially on ocular lenses is one of themain arguments pointed out against wide application of the same.

From the medical point of view this fact has to be carefully considered,since among prevailing saprophytic species of fungi some have beenisolated (mostly of Aspergilus tribe) which are Well-known parent ofserious mycotis effects. Nevertheless even the non-pathogenic species offungi can cause in the delicate ophthalmic medium a hypersensitivity tosome of their somatic components as well as to their metabolites.

The aforesaid problem cannot be solved in that the lenses would beoffered for sale safely sterile in suitable well-protecting packing, or,on the other hand, that they would be vended in dry state. The maintroubles with the lenses will arise in applying them, since theoptician, or oculist is not in a position to keep a large store oflenses in open state with the danger that they become degraded by anattack of molds or fungi. After all in this case even the patient wouldhave to sterilise his lenses every two or three days in boiling water.Such an operation is rather tedious both for the patient and theoptician, since the lenses for their smooth surface have to be boiledoff separate lest they might get fused.

A similar practice is to be kept if storing other products made ofhydrogels, such as, for example, prostheses of blood vessels, mammae,urinal ducts, pharynx, some substitutes for filling somatic cavities,prostheses of peritonaeum and other membranes, or ophthalomologicprostheses, and the like. In some of the said applications thehydrophilic gel has not to be dried up even in the preparation stage,since especially porous. hydrogels lose permanently their porosity whendried.

conventionally employed fungicidal and disinfecting agents cannot beused for the medical application of hydrophilic gels, since when appliedin effective concentrations they may cause heavy irritations of thehuman eye, and moreover some of them are well-known as causingfrequently allergic effects which .in some cases may be fatal. This facteliminates practically the application of all agents having generalantimycotic effects. The hereinbefore said drawbacks are overcomeaccording to the present invention by storing hydrophilic gels in asystem consisting of a receptacle of which the inner room is divided atleast into two compartments. In one of them the hydrophilic material isstored under water or an aqueous solution while in the other, separatedfrom the former by a permeable partition and communicating therewith,there is deposited a water-swellable polymer containing surface-activesilver. The shape and arrangement of the system for storing hydrophilicgels can vary according to different application purports.

EXAMPLE 1 The most simple system to be employed consists of a little bagmade of a porous, for example textile fabric manufactured of e.g.polyamide, polyester, cotton, and the like, which bag is filled up witha strongly acidic styrene divinyl-benzene cation exchanger which hasbeen saturated with a solution of silver nitrate whereupon silver wasreduced for inst. by means of hydrazine hydrate. The bag of anappropriate size is then put in a receptacle, the hydrophilic gel beingstored above the same. For storing ocular lenses by the patient theremay preferably be used a double system comprising two compartments eachto receive one lens, and a central compartment between two perforatedwalls designed for silvered cation exchanger, the receptacle beingprovided with stoppers on either side.

EXAMPLE 2 For opticians practice there may be recommended well knownplain containers made of polystyrene, where silvered cation exchanger isdeposited under a false bottom. Alternately, well-known receptacles madeof plastic, such as, for example, polypropylene, can be used forstoring. For processing conditions it is advantageous to employ, forinstance, a tank provided with a false bottom, the silvered cationexchanger being kept in the lower part thereof, in a bag, or in bulk, asreferred to in Example 1, while in the upper portion there is arranged adevice for depositing, or hanging up the hydrophilic articles to bestored. The protective system can be attached to a machine formanufacturing contact lenses, or hydrogel prostheses, preferablyadjacent the moulds, since the hydrophilic products may be attacked byfungi within a period of being taken off from the moulds. The reductionof silver is carried out by any of Well-known methods, such as, forexample, by means of hydrazine hydrate in an alkaline solution, or bymeans of other strongly reducing agents.

EXAMPLE 3 Strongly acidic styrene divinylbenzene cation exchanger isregenerated in a column by 10 percent hydrochloric acid into Hplus form,and rinsed with diluted 5 percent nitric acid and finally With water upto the neutral reaction. Thereupon it is converted to Ag-form byreacting with diluted 5 percent silver nitrate and rinsed with distilledwater. The cation exchanger will then be taken olf from the column andflooded with double volume of percent hydrazine sulphate solution inpercent aqueous ammonia. After the nitrogen evolution has been finishedthe cation exchanger together with the reduced silver will be washedthrough by water-decanting up to the last of the reaction to ammonia.The water layer above the cation exchanger must not react to ammoniaeven after a fortnights standing. The reduction of silver can beperformed even by other methods, such as, for example, by means offormaldehyde, hydroquinone, glucose, and the like.

As cation exchanger there may be used a sulphonated styrenedivinylbenzene polymer, preferably macroporous, or a carboxylic cationexchanger, e.g. on the basis of a co-polymer of methacrylic acid withdivinylbenzene. The polymeric ion exchanger lattice is absolutelyinsoluble, guaranteeing thus that human organism could not be affected.Phenolic polycondensed cation exchangers cannot be applied for thepurpose without being previously tested, since they may make freephenols which penetrate into the surrounding solution.

The grain size of the cation exchanger is to be selected in a suitablerange lest individual grains might penetrate through the bag walls. Thebags may be manufactured in any of well-known manners, such as, forexample, by stitching both edges of a plied endless belt lengthwisetogether, further by a number of spaced transverse stitches, by cuttingthe stitched belt lengthwise in the middle, filling up the bags formedin such a way with the respective cation exchanger, and finally bystitching both free remaining edges together again.

A very convenient form of silvered cation exchanger is a membrane whichcan be cut to pieces which are then lodged under the false bottom orbetween two perforated partitions of the receptacle. Another embodimentconsists in lining at least a part of the receptacle for the hydrogelwith a silvered cation exchanger. The effect of the silver cationexchanger can be proved by a number of tests as follows:

II Lenses in physiologic solution inoculated with a mold culture.

III Leuses in physiologic solution Lenses absolutely intact.

plus Ag-cation exchanger.

IV Lenses in physiologic solution Lenses absolutely intact inoculatedwith a mold without traces of fungi culture plus Ag-cation growth.

exchanger.

With the above reference Groups I and II an intense up to mass attack ofthe lenses by molds occurs. On the other hand, with the test Groups IIIand IV where Agcation exchanger was used the lenses were perfectlylimpid and intact, both macroscopically and microscopically. Thus thesilvered cation exchanger meets all conditions to be laid down with aprotective agent for disinfecting the material to come into contact withhuman organism, e.g. with the eye. Moreover silver cannot be found inthe solution by using any of conventional analytic methods, and also noharmful eifects thereof on human organism were recorded. The silvercation ex- 4 ing aqueous liquid and penetrate into the hydrogel so thateven spores in the swollen gel are killed when budding.

In the preparation of the contact ocular lenses as well as ofhydrophilic methacrylate gels in general, the use of the silver cationexchanger is connected with the following advantages:

(i) The interval between the preparation and packing of the lenses canbe extended whereby it is possible to obtain far better liberation ofthe lenses from any undesirable soluble substances. The lenses are notthreatened with attack of molds and fungi before being packed.

(ii) The method enables to save two or three packers over the methodsused heretofore.

(iii) Colour shades on the lenses, eye-burning, and

changes of dioptric values are eliminated.

(iv) The lenses can be perfectly sterilized when used by the patient whoneed not now sterilize them by boiling.

(v) The opticians and oculists manipulation with the lenses is madeeasier, since heretofore it has been necessary to employ at least oneassistant to sterilize the lenses ready for application.

(vi) The main argument against wide practical application of the lensescan be disproved.

(vii) When using silvered cation exchanger together with physiologicsolution the lenses can be applied directly on to .the eye-ball withoutadditional washing.

What we claim is:

1. Apparatus for the storage of a swellable hydrophilic polymeric gelbody such as a contact lens or other implant comprising a liquidcontainer divided into at least two parts by a porous wall and having aphysiologic liquid contained therein, one of said container parts beingadapted to hold said gel body immersed in said liquid, a cation resinexchange material impregnated with a surface active metallic silver,said material being located in the other of the container parts andbeing soluble by liquid to release surface silver ions over a period oftime to thereafter, freely flow through said porous wall into contactwith said gel body.

2. The apparatus according to claim 1 wherein said exchange material isformed as a plurality of soluble beads, said beads being held in aporous fabric bag. 7

3. The apparatus according to claim 1 wherein said exchange material isformed as a membrane sheet.

4. The apparatus according to claim 1 wherein the resin exchangematerial comprises a strongly acidic styrenedivinyl-benzene containingsurface active metallic silver.

5. The apparatus according to claim 4 wherein said resin exchangematerial is macroporous.

References Cited UNITED STATES PATENTS 1,883,967 10/1932 Krause 21-91X2,066,271 12/1936 Irwin 424132 2,121,875 6/1938 Kruse et al. 2158X2,283,883 5/1942 Conconi 424132 2,347,567 4/1944 Kresse 424-1322,595,290 5/1952 Quinn 424-132 3,092,552 6/1963 Romans 424-432 3,211,28110/1965 Speshyock et al 2065A 3,220,960 11/ 1969 Wichterle et a1 351MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, Assistant Examiner

